'99 Z28 odometer registration problem?
02-12-2013, 07:51 PM
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'99 Z28 odometer registration problem? I recently purchased a 1-owner Z28 with 34000 verified miles. Car has not been modded other than a Magnaflow exhaust and 17" Corvette 5 spokes with 245/45-17 tires. Car is near perfect and runs great but my concern/question is: it seemed like the speedo was indicating what I felt was a higher speed than I was traveling. Today, I checked the odometer against the mile markers on my way to work and it is indeed recording about 1/10th per mile too fast. Can the change in wheel/tire size from stock be this drastic?
02-12-2013, 08:22 PM
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It is possible OP. But did your car not come stock with 17'' rims. If it came equipped with 16'' then the rim size could be a factor.
I can tell you from experience that when I changed my rear gear ratio from 3.42 to 3.90 that I had the exact same issue you have. It's possible that you have a different gear ratio and different than stock tire size. Unfortunately the only way to correct is to change all components back to stock OR get some sort of tune to correct your speedo. Any handheld tuner that you buy can fix it, but the best/cheaper route would be to have a mail order tune done. Cheaper and it will make some more power as a bonus. Search for "Frost tunes" on this site and he can get you all set. OP sorry for the long reply, just wanted to give you all the info. Hope this helps.
I can tell you from experience that when I changed my rear gear ratio from 3.42 to 3.90 that I had the exact same issue you have. It's possible that you have a different gear ratio and different than stock tire size. Unfortunately the only way to correct is to change all components back to stock OR get some sort of tune to correct your speedo. Any handheld tuner that you buy can fix it, but the best/cheaper route would be to have a mail order tune done. Cheaper and it will make some more power as a bonus. Search for "Frost tunes" on this site and he can get you all set. OP sorry for the long reply, just wanted to give you all the info. Hope this helps.
02-13-2013, 12:10 AM
#4
It is possible OP. But did your car not come stock with 17'' rims. If it came equipped with 16'' then the rim size could be a factor.
I can tell you from experience that when I changed my rear gear ratio from 3.42 to 3.90 that I had the exact same issue you have. It's possible that you have a different gear ratio and different than stock tire size. Unfortunately the only way to correct is to change all components back to stock OR get some sort of tune to correct your speedo. Any handheld tuner that you buy can fix it, but the best/cheaper route would be to have a mail order tune done. Cheaper and it will make some more power as a bonus. Search for "Frost tunes" on this site and he can get you all set. OP sorry for the long reply, just wanted to give you all the info. Hope this helps.
I can tell you from experience that when I changed my rear gear ratio from 3.42 to 3.90 that I had the exact same issue you have. It's possible that you have a different gear ratio and different than stock tire size. Unfortunately the only way to correct is to change all components back to stock OR get some sort of tune to correct your speedo. Any handheld tuner that you buy can fix it, but the best/cheaper route would be to have a mail order tune done. Cheaper and it will make some more power as a bonus. Search for "Frost tunes" on this site and he can get you all set. OP sorry for the long reply, just wanted to give you all the info. Hope this helps.
02-13-2013, 08:32 AM
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I agree.
Wheel size would have nothing to do with this since the OP mentioned having 245/45/17 tire size, which equals 25.68" diameter.
Stock tire sizes are:
245/50/16: 25.65" diameter
275/40/17: 25.66" diameter
All that matters in this regard is overall tire diameter, not wheel size. And the difference between all three of these tire sizes is not enough to cause a false speedometer reading.
Now if the gears have been swapped without any recalibration of the speedometer, then the readings could/would certainly be incorrect.
02-13-2013, 10:26 AM
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If you have a smart phone you can download a free GPS speedometer app. Them you'll know how far off yours really is, if it's a significant amount then chances are your car has different gears.
02-16-2013, 11:42 AM
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I recently purchased a 1-owner Z28 with 34000 verified miles. Car has not been modded other than a Magnaflow exhaust and 17" Corvette 5 spokes with 245/45-17 tires. Car is near perfect and runs great but my concern/question is: it seemed like the speedo was indicating what I felt was a higher speed than I was traveling. Today, I checked the odometer against the mile markers on my way to work and it is indeed recording about 1/10th per mile too fast. Can the change in wheel/tire size from stock be this drastic?
